Evaluation of the Clinical and Economic Burden of Poor Glycemic Control Associated with Therapeutic Inertia in Patients with Type 2 Diabetes in the United States

Therapeutic inertia has been defined as a failure on the part of healthcare provider to initiate or intensify therapy when needed [27] and has been shown to exist at all stages of the diabetes treatment paradigm, although therapeutic inertia toward the initiation of insulin is particularly pronounced [6, 28‐30]. This is one of the first analyses to provide US-specific quantitative estimates of the economic implications of delayed treatment intensification due to therapeutic inertia on both an individual patient and population level. Specifically, over a time horizon of just 1 year and assuming a baseline HbA1c of 9.0% (75 mmol/mol), a 1-year delay in treatment intensification was associated with an additional economic burden of USD 7.3 billion, including USD 1.8 billion due to diabetes-related complications. These population estimates are based on reports of the prevalent population of type 2 diabetes patients in 2017. In the USA, the absolute number of people living with type 2 diabetes is projected to almost double by 2030, meaning that the economic burden associated with delayed treatment intensification is likely to increase considerably over the next decade.

Alongside the economic burden, the clinical implications of delayed treatment intensification are also considerable. A 1-year delay in intensification from 9.0% to a target of 7.0% was projected to cost the population 642,699 years of life over a 30-year time horizon. The impact of poor glycemic control projected here is, on an individual patient level, aligned with data reported previously. For example, in a UK-based analysis, Paul et al. [31] reported that for patients with HbA1c ≥ 7.0% (53 mmol/mol) (versus < 7.0%) a 1-year delay in treatment intensification was associated with a 67% increase in the risk of myocardial infarction and a 51% increase in the risk of stroke. Similarly, a 2017 modeling analysis, conducted using the Archimedes model, also reported a higher incidence of complications with delayed intensification [32].

In the present analysis, the consequences of intensification delays ranging from 1 to 7 years were explored, which is in line with those reported in routine clinical practice. In one UK-based analysis, the median time to intensification for patients on one, two, or three oral antidiabetes drugs (OADs) at baseline was 7.1, 6.1, and 6.0 years, respectively, and the mean HbA1c at the time of intensification was 8.7% (72 mmol/mol), 9.1% (76 mol/mol), and 9.7% (83 mmol/mol), respectively [29]. In a second UK-based study, Khunti et al. [30] reported that among insulin-treated patients with poor glycemic control (defined as HbA1c ≥ 7.5% [58 mmol/mol]) who did undergo treatment intensification, the median time to intensification was 3.7 years and mean HbA1c at intensification was > 9.0% (75 mmol/mol). Additionally, it should be noted that the time frame of most clinical studies examining delays in intensification is such that, typically, only a short temporal window in the overall treatment paradigm is included in the analysis. As type 2 diabetes is a progressive disease, therapy has to be routinely intensified multiple times over a patient’s lifetime to maintain good glycemic control and mitigate the risk of diabetes-related complications. There may well be intensification delays at each stage, meaning that the cumulative time spent in poor glycemic control may be longer than that reported in individual studies [33]. The cumulative time spent with poor glycemic control was examined in a US-based analysis by Brown et al. [34], who estimated that even in a well-controlled population, OAD-treated patients spent a mean time of almost 5 years with HbA1c > 8.0% (64 mol/mol) prior to insulin initiation. Notably, this analysis was limited to patients treated with OADs and does not capture potential further cumulative time spent in poor glycemic control associated with any delays in intensification of therapy once patients initiated insulin.

The present analysis uses HbA1c targets that are aligned with previously published recommendations, e.g., the ADA targets of 6.5% (48 mmol/mol), 7.0% (53 mmol/mol), and 8.0% (64 mmol/mol) selected according to individual patient characteristics [15]. In the most recent consensus report by the ADA and the European Association for the Study of Diabetes (EASD), the focus is on individual targets for each patient, stating that a “reasonable HbA1c target for most non-pregnant adults with sufficient life expectancy to see microvascular benefits (generally ~ 10 years) is around 53 mmol/mol (7%) or less”, and noting that targets should be individualized on the basis of patient preferences, treatment goals, and the risk of adverse effects of therapy [4]. While therapy targets are moving away from fixed HbA1c goals at the individual patient level, the use of such threshold values at a population level is still helpful in terms of understanding the benefits of new therapies in a given population, and for quantifying the burden of poor glycemic control. Moreover, the approach of using glycemic control thresholds for a population is aligned with previous publications on therapeutic inertia [26, 27, 34].

Therapeutic inertia may arise at the patient, physician, or healthcare system level, or may be multifactorial emanating at a number of different levels. Barriers to treatment intensification at the patient level include a reluctance to initiate injectable therapies, poor health literacy, increased costs, unwillingness to undertake a more complex regimen, and fear of weight gain with insulin. At the physician level, fears over hypoglycemia have been documented specifically with regard to insulin initiation or intensification. Additionally, therapeutic inertia in relation to the initiation of insulin has been reported to be more common in primary care than for patients treated by secondary care specialists [35]. Moreover, a number of studies have reported similar therapeutic inertia in patients receiving OADs, suggesting that therapeutic inertia can lead to poor glycemic control across the treatment continuum [33]. Concern over increasingly complex regimens negatively influencing adherence has also been reported to contribute to therapeutic inertia at the physician level [36, 37]. The present analysis has shown that treatment delays of even 1 year, and the resultant time spent with poor glycemic control, are associated with substantial clinical and economic consequences. As such, initiatives aimed at overcoming therapeutic inertia both at the patient and physician level are likely to play an important role in combating the increasing burden of disease associated with type 2 diabetes. Initiatives that have been documented as helping overcome therapeutic inertia include patient education programs, simplifying treatment or titration regimens, and the inception of nurse practitioner-led diabetes care, with frequent follow-up allowing for the establishment of good patient–healthcare provider relationships and continuity of care as well as reassurance and assistance with issues such as timing and dosing of new therapies, management of treatment-related adverse events, and titration of insulin [36]. In a recent review, Okemah et al. [38] noted that therapeutic inertia results from healthcare provider-, patient-, and healthcare system-based factors, and represents a serious barrier to optimal treatment escalation and, as a result, glycemic control. The complex nature of inertia means that addressing it requires a combinatorial approach. The authors cited evidence supporting the role of patient education and involvement, personalizing therapy, patient feedback, education of healthcare providers and use of clinical decision support tools to reduce therapeutic inertia and improve outcomes for patients with type 2 diabetes.

The present study is associated with a number of limitations. Only costs associated with long-term diabetes-related complications were considered in the analysis. Costs associated with treatment (OADs and insulin) were not considered. Additionally, the clinical focus of the analysis was limited to HbA1c alone. Although there may be covariance between HbA1c and other physiological risk factors (such as lipid levels and systolic blood pressure) and management of these risk factors is an integral component of diabetes management, HbA1c was the only risk factor captured in the analysis. While this may present an overly simplistic picture of disease management, the rationale for this was that it permitted a focused analysis of HbA1c alone. The costs and quality of life deficits associated with hypoglycemic events were also not included in the current analysis. For patients with problematic hypoglycemic events, individualized HbA1c targets may be above the 7.0% (53 mmol/mol) threshold used here. The omission of hypoglycemic events should be noted when considering findings, particularly on an individual patient level. Allied to this, it should be noted that on an individual patient level, there are other circumstances in which physicians may tolerate poor glycemic control or set HbA1c target levels above 7.0% (53 mmol/mol); these may include instances where the patient has limited life expectancy or cases where multiple serious comorbid conditions are present.